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Insulation on steel supports


Feeby100

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1 minute ago, Feeby100 said:

I have insulation in the form of kingspan 

and there are steel supports level with it 

can I put roll silver insulation on them with foil tape ? 

 

 

Of course you can - it is your boat you can do what you want with it.

When you cover it up no one will be any the wiser.

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I'm not sure about this, you need to find out more. Aluminium insulation is a bit odd because Ali is actually a good conductor of heat so maybe this stuff is really to reflect heat in some way rather than proper insulation.

The danger is that the foil on the Kingspan is likely a good heat conductor, your proposed insulation is a good conductor, and foil tape is a good conductor, so linking these to the exposed steel will just allow heat to conduct from inside the boat to the bare steel so undoing the insulation of the Kingspan. In effect you might turn a small "cold bridge" into a much bigger one.

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It is essential to cover any steel with at least 25mm of foam or wood lath, 50mm is bette,r otherwise you will get stripes of condensation across the lining then it will stain and maybe even drip and you really don't want to get all that bother. 

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Ok thanks but I have no option as need to just cover with something before T&g over it 

when I striped it out it only had a 3 mm of Polystyrene strip glue to it and the wood above was absolutely fine and it was for 30 years

Edited by Feeby100
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2 minutes ago, Feeby100 said:

Ok thanks but I have no option as need to just cover with something before T&g over it 

 

That Ali insulation claims that its about 4mm thick and gives insulation equivalent to 55mm of polystyrene. This just can't be true, in fact its way off, they must have found some kind of technical loophole so they can say this stuff legally. Like wot I said, as Ali conducts heat in your application it might actually be (literally) worse than useless. 

How much space have you got between the steel stiffeners and the T&G roof lining? Could you get something about 20mm thick in there?, or even 10???

 

 

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48 minutes ago, Feeby100 said:

Ok thanks but I have no option as need to just cover with something before T&g over it 

when I striped it out it only had a 3 mm of Polystyrene strip glue to it and the wood above was absolutely fine and it was for 30 years

That is what I put on the wooden battens on my steel before fixing the ply and MDF I can see on the ceiling where the cross beams are. I used the stuff to go behind wall paper

https://www.amazon.co.uk/Erfurt-Mav-Polystyrene-Wall-Insulation/dp/B006UFLBIO

other makes available

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ok  my boat is similar and in winter that 3mm polystyrene gets waterlogged, expanded polystyrene is not 100% waterproof. Did you have any rust on the steel frame?

 

As you intended to put that ali stuff in you must have a bit of space. Have you got 6mm?  Extruded polystyrene might just work (much better than expanded) Danger is if you totally close the air gap then any condensation (or leaked water) might get trapped. If all else fails then thin hardwood strips are probably better than bare steel.

Aerogel is worth investigating, a great insulator, very expensive, and not fully waterproof.

In fact Aerogel is THE best insulator, but still not as good as that ali stuff claims to be 😀.

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As Dave says, that silver insulation stuff only works because the aluminium is a bad radiator of heat. So in order to work, it needs to have an air gap preferably on the cold side. If you put it between the Kingspan (which already has a reflective surface) and the lining with no air gap, it will be pretty much useless.

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28 minutes ago, Feeby100 said:

found this ? 
 

18568EE0-0FCE-4947-821C-ECBAA711C809.png

 

I really can't say, graphite giving a 20% improvement is no big deal, going for extruded polystyrene is probably still better. It all comes down to what the "laminate" is made off and they don't give details. If its proper waterproof then with careful installation this stuff might be much better than nothing, but if its heat conductive then again it might be worse than useless.

The big problem is that expanded polystyrene is not 100% waterproof so in winter some water will get sucked in, and if the stuff is only a few mm thick this water penetrates right through so it looses all its insulation properties and can also be a source of rust.

Extruded polystyrene is much more waterproof, Kingspan etc is better in many ways, but I think is only available from 20mm thick whilst extruded polystyrene is available down to 6mm.

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13 hours ago, Feeby100 said:

Ok thanks but I have no option as need to just cover with something before T&g over it 

when I striped it out it only had a 3 mm of Polystyrene strip glue to it and the wood above was absolutely fine and it was for 30 years

So why not do the same again?

It's the technique Graham Booth recommends in The Narrowboat Buioders Book. I would be minded to use two layers of the thin sheet polystyrene you can use under wallpaper, and glue it on with heavy duty wallpaper paste. The timber lining, once fixed, will hold it in place long term.

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1 hour ago, David Mack said:

So why not do the same again?

It's the technique Graham Booth recommends in The Narrowboat Buioders Book. I would be minded to use two layers of the thin sheet polystyrene you can use under wallpaper, and glue it on with heavy duty wallpaper paste. The timber lining, once fixed, will hold it in place long term.

 

Speaking from recent personal experience the very thin stuff will become waterlogged in winter and let rust get through (as its effectively standing water)

'We are done with thin stuff under the gunnels and on the roof framing and I am slowly working through the boat (where I have access) and fixing it. Its probably 2 or 3mm thick and I conclude that is just not enough.

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